Table 2.

Femoral stem survival: 98.83% cumulative survival for the stem alone

Years since operation	Number at start	Failure	Withdrawn	Number at risk	Effective number at risk	Annual failure rate (%)	Annual success rate (%)	Cumulative survival rate (%)	95% lower bound	95% upper bound
0–1	89	0	3	87.5	87.50	0.0000	1.0000	1.0000	0.9579	1.0000
1–2	86	1	1	85.5	86.49	0.0117	0.9883	0.9883	0.9372	0.9979
2–3	84	0	3	82.5	85.12	0.0000	1.0000	0.9883	0.9365	0.9979
3–4	81	0	2	80	83.78	0.0000	1.0000	0.9883	0.9358	0.9980
4–5	79	0	1	78.5	82.67	0.0000	1.0000	0.9883	0.9353	0.9980
5–6	78	0	1	77.5	81.76	0.0000	1.0000	0.9883	0.9348	0.9980
6–7	77	0	3	75.5	80.80	0.0000	1.0000	0.9883	0.9343	0.9980
7–8	74	0	4	72	79.58	0.0000	1.0000	0.9883	0.9336	0.9980
8–9	70	0	12	64	77.49	0.0000	1.0000	0.9883	0.9324	0.9981
9–10	58	0	14	51	73.66	0.0000	1.0000	0.9883	0.9301	0.9981
10–11	44	0	18	35	66.94	0.0000	1.0000	0.9883	0.9253	0.9983
11–12	26	0	5	23.5	58.00	0.0000	1.0000	0.9883	0.9175	0.9984
12–13	21	0	8	17	48.93	0.0000	1.0000	0.9883	0.9069	0.9986
13–14	13	0	5	10.5	38.79	0.0000	1.0000	0.9883	0.8897	0.9989
14–15	8	0	5	5.5	27.64	0.0000	1.0000	0.9883	0.8583	0.9992
15–16	3	0	3	1.5	13.23	0.0000	1.0000	0.9883	0.7573	0.9996